1. Field of the Invention
The present invention relates to a rubbing system for an alignment layer of a liquid crystal display (LCD) device, and more particularly, to a rubbing system for an alignment layer of an LCD device capable of quickly and effectively controlling a gap between a rubbing roll and an alignment layer by moving the rubbing roll and a rubbing table, and capable of providing a uniform alignment controlling force to the alignment layer, and a method thereof.
2. Discussion of the Related Art
Recently, various portable electronic devices, such as mobile phones, personal digital assistants (PDAs), and note book computers have been developed, because of their light weight and compact sizes and power efficiency. Accordingly, flat panel display devices, such as liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and vacuum fluorescent displays (VFDs), have been developed. Of these flat panel display devices, LCDs are currently mass produced because of their driving capabilities and superior image quality.
The LCD device may be classified as a transmissive type display device. LCDs display an image by controlling the amount of light that passes through a liquid crystal layer according to an initial alignment direction. Therefore, it is necessary to process an alignment layer of the LCD device so that liquid crystal molecules can initially have a uniform direction. Various methods for processing an alignment layer have been implemented. Among the various methods, the most frequently used method is a method for processing an alignment layer by rubbing. In the rubbing alignment processing method, an alignment layer is formed on a substrate and rubbing is performed by using an alignment material, thereby forming uniform microstructures on the alignment layer. As the alignment layer and liquid crystal molecules interact with each other by application of an alignment controlling force to the liquid crystal molecules, the liquid crystal molecules can be uniformly aligned on the entire surface of the alignment layer in a desired direction.
However, the method for processing an alignment layer by rubbing has the following problems. Rubbing is performed by contacting a rubbing roll, on which a rubbing material is wound, with the alignment layer that is formed on a substrate and then moving the rubbing roll in one direction. Because LCD devices are not only portable devices such as notebooks but can also include large electronic devices such as a television, etc., a size of the LCD device naturally increases (a mother substrate for fabricating a liquid crystal panel is larger in large devices). Therefore, width and weight of the rubbing roll are increased when an alignment layer of a large LCD device is processed by rubbing.
An alignment controlling force or a surface fixing force of the alignment layer rubbed by the rubbing roll are a function of microstructures formed on the alignment layer. Also, microstructure depth is varied according to pressure of the rubbing roll applied to the alignment layer. As width and weight of the rubbing roll are increased, uniformly maintaining a pressure applied to a mother substrate is difficult. Lack of uniform pressure applied to the mother substrate can result in defects on the alignment layer.